Can steel be anodized? If so, how?

Q. Is there a process to anodise steel or cast iron? If not, what can be done to achieve similar results?

Josh JonesAftermarket Manufacturing - Flint, Michigan

(2005)

Q. Ours is an Aluminium Extrusion and Finishing Company. We have the anodizing facility for aluminium profiles using sulphuric acid. We do get enquiries for anodizing steel. But our sulphuric acid process is not suitable for steel.

Can anyone give some guidelines / process (suitable electrolyte and other data) to carry out industrial anodizing of steel?

Thanks,

MANALEL CHACKO NINANEXTRUSIONS - DUBAI, DUBAI, U.A.E.

(2005)

A. Hi Josh; hi Manalel. Aluminum oxide can form a tight, tenacious, corrosion resistant coating on aluminum, such that aluminum can be beneficially anodized. But iron oxide (rust) will not to my knowledge form a tight, tenacious, corrosion resistant coating on steel, so I don't think it can be beneficially anodized.

I don't know what you have in mind by 'similar results'. Nitriding would give a wear resistant surface, but it is conductive (unlike anodizing which is an insulator); further, it cannot absorb dye. Paint, powder coating, or electrophoretic lacquering might do what you want but would not be as hard or wear-resistant as anodizing. Certain platings might achieve what you could be looking for. If you can detail what characteristics you are looking for, people can possibly direct you to finishing processes that might deliver them.

Ted Mooney, P.E.finishing.comPine Beach, New Jersey

Can't find electrophoretic lacquering services

April 6, 2018

Q. Hello, Ted Mooney posted in 2005 that there was a coating called electrophoretic lacquering, I tried to look it up and all I got was companies across the seas. Is there anyone here in the US that handles this and the process it takes? I work for a small welding/fabrication shop and I was thinking of trying this if it was not too costly to start up.

A. Hi Jeffrey. "Electrophoretic lacquering" has a lot of synonyms, which is probably what is making it hard for you to find suppliers. It also goes by the names e-painting, e-coating, electropainting, electrocoating, and electrophoretic coating. In the old days, the work was usually anodic but the great majority of it today is done with the work being cathodic, leading also to the terms cathodic electrodeposition or CED coating.

Most of the time electrocoating is done as a primer coating (all automobile and truck bodies are electrocoated to my knowledge). When it is done as a final decorative coating, people like myself might sometimes call it "electrophoretic lacquering" to sort of imply that in this application we want it to be decorative. If you use that list of synonyms you will find dozens of threads on that topic on this site, and if you google for terms like 'decorative electrocoating' you can probably find suppliers.

A. Anodizing forms an oxide protective barrier on aluminum but if you form iron oxide over steel it will not protect it adequately, for that reason a different compound has to be developed. You may want to explore blackening, galvanizing or phosphate coating of steel.

Guillermo MarrufoMonterrey, NL, Mexico

(2005)

A. Hi.
Some companies claim that they know an Electrochemical Process for stainless steel wherein Chrome Oxide can be produced/enhanced and by varying the thickness it attains different color. Maybe you are talking about that? But, to the best of my knowledge, the term "Anodizing" is used only for Anodizing of Aluminum.

Thanks,

Keshava Prasad M- Chennai, India

(2005)

A. You do not want to want to make the surface of steel more anodic. To protect it, it should have a continuous cationic coating.

Fred N. Teumac- Fort Myers, Florida, USA

? Hi Fred. I don't understand that one at all. Are you suggesting cataphoretic electrocoating (CED)? Please expound. Thanks.

Regards,

Ted Mooney, P.E.finishing.comPine Beach, New Jersey

December 16, 2008A. Hi.
Anodizing is used only for Aluminum, but for steel you can use metal spray (with Aluminum wire) over it.
After that you can Anodize it.
Good luck

From a quick review it doesn't look like a process which will offer a hard and wear-resistant surface, or even a very corrosion resistant one, but I find it intriguing as an alternative to phosphate pretreatment before painting -- especially for the short sighted 'environmentalists' who see an ounce of phosphate as a problem, but not the multiple re-mining, re-smelting, re-fabricating, re-painting, re-shipping, re-selling, and re-landfilling operations for a ton of steel constantly replaced due to inferior non-phosphate pretreatment :-)

Regards,

Ted Mooney, P.E.finishing.comPine Beach, New Jersey

January 28, 2013

Q. Dear Sir
Can you (please) send me the relationship between Time & Voltage for steel anodizing?
I am a student to get MS.c in chemical engineering -- Anodizing of steel.
Thank you
Best regards,

Basheer Ahmed- Baghdad-Iraq

A. Hi Basheer. There is no such commercial process. But you might wish to review the previously suggested pdfs for experimentation purposes.

Regards,

Ted Mooney, P.E.finishing.comPine Beach, New Jersey

November 30, 2013

Q. Dear sir,
Our company is consistently producing case hardened kingpins (knuckle pins for trucks & bus). The final finishing of these kingpins are either grinding (only) or Hard chrome plating and grinding.

Recently, our competitor introduced a very hard black (very deep greenish) and corrosion resistant coated kingpin in the market and is dramatically establishing an upper hand. It seems their kingpins are hard-Anodized or something like it (I am confused and getting hopeless gradually). But I again learned that, only Aluminum can be anodized. Or it may be a phosphate coating over the Case hardened steel.
Any kind advice would be appreciated with gratitude.

Thanks.

Muhammed Hanifaengineering works - Pabna, Rajshahi, Bangladesh

November 2013

A. Hi Muhammed. Yes, it is indeed easy to get confused about whether steel can be anodized because it depends on exactly what you mean by "anodized" :-)

- If we mean "can it be immersed into a conductive liquid and be attached to the positive pole of the circuit to a beneficial purpose", the answer is a qualified yes because it seems that anodizing of steel is a development laboratory idea as a possible pretreatment option before painting, or for coloring weathering steel, but it is not a commercial practice.

- If we mean can we get similar properties to what we get from sulfuric acid anodizing of aluminum (hard, wear-resistant, dyeable, insulating, highly corrosion resistant) the answer is a clear no.

Trying to guess what your competitor is doing from the color of the coating may not get you too far. But might it be a QPP salt-bath nitriding process? Or a solid-film lubricant process? What properties does it offer that the customers are finding attractive?

In that case I would think that their product is carbonitrided, or nitrocarburized, both of which mean almost the same thing. And ... it's fairly deep, maybe .010" to .025"

That's the only way I know of to beat carburized and hardened and hard chrome.

Jeffrey Holmes, CEFSpartanburg,
South Carolina

January 1, 2014

Q. Hello sir,
your assumption on "what my competitor is doing" was exactly right & helpful. Their kingpins are in fact quench:polish:quench nitrocarburized. Thanks.
I have already contacted the nearest HEF Durferrit agent. They can supply us with the required chemicals for the surface treatment process. My point is, will it be optimum, if I purchase their chemicals for our requirement?
THANKS again for supporting us from your immense experience.

Q. A few years ago Mr.Josh Jones asked about a process of anodizing steel to achieve "similar" results.

I write a blog about cookware of all types, most of which have been created to eliminate the drawbacks of using steel to construct bakeware and cookware.

Is there a food grade process, similar to anodizing, where steel can be made corrosion free, where the food will be easy to release and the pan or pot be easy to clean?

Tin was an attempt, vitreous enameling is an attempt, but these are applied coatings.

Thanks for your consideration.

Richard PoussonBakeware/Cookware Blogger - Concord, California

May 2016

A. Hi. I do not believe there is any mechanical finishing process or conversion coating process which can make a steel pot into appropriate bakeware or cookware ... but as you mention, there are various coating processes that will do so.

Q. Hi
My project about anodized iron.
The data could not find a way to do it, someone has a better solution?

shahin zaresharif university - Tehran, Iran

July 2016

A. Hi Shahin. The previously offered pdfs from New Mexico Tech seem to explain all of the solutions they tested as well as their exact preferred embodiment. I do not understand what you mean about not being able to find a way: please clarify.

What are you expecting from the process; what properties are you looking for; what are you doing; what are you attaining? Let's not run in circles please, but try our best to move forward based on what has already been said :-)

A. Hi Randy. I don't know what finish is on your cast iron parts, but it's certainly not anodizing. If they are not plated with anything, just bare cast iron, phosphatization would be the normal pretreatment. You can't do true phosphatization yourself, but you can apply Naval Jelly [linked by editor to product info at Amazon] which is the consumer's best imitation of a phosphatized coating.
If the parts are plated with something like zinc, nickel, or chrome, you could try an adhesion promoter =>
But if that doesn't work well enough (and it probably won't work great), you would probably have to remove the plating before painting, or have the parts replated instead of repainted. Good luck.

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